Thermocouple unit



Sept. 29, 1953 S. G. BEST THERMOCOUPLE UNIT Filed Nov. 28, 1951 INVENTORSTANLEY 3. BEST frZ/Mh Q W ATTORNEY Patented Sept. 29, 1953 THERMOCOUPLEUNIT Stanley G. Best, Manchester, Conn, assignor to United AircraftCorporation, East Hartford, Conn., a corporation of Delaware ApplicationNovember 28, 1951, Serial No. 258,717

4 Claims.

This invention relates to thermocouple units and particularly to themechanical structure and arrangement of the thermocouple.

An object of this invention is to provide a thermocouple suflicientlyrugged to withstand the severe operating conditions found in jetengines.

A further object is to provide a thermocouple in which the thermocouplewires and the hot junction are rigidly supported and amply protectedagainst both radiation and mechanical damage.

A further object is to provide a hot junction having a large area tomass ratio.

A still further object is to provide a thermocouple which can be easilyassembled and in which a faulty junction may be scrapped before assemblywithout the necessity of scrapping the entire assembly Additionalobjects and advantages may be ascertained from the followingspecification and the accompanying drawings in which,

Fig. 1 is a side view partly in section of the completely assembledthermocouple.

Fig. 2 is a longitudinal section taken on the line 2-2 of Fig. 1.

Fig. 3 is a horizontal sectional view taken on the line 3-3 of Fig. 1.

The invention is shown in the drawing as incorporated in a thermocoupleadapted for use in a jet engine and comprising in general a supportingtube in which a pair of wires 12 and ll of suitable dissimilar metalsare supported. One of the wires may be made of Chromel and the other ofAlumel. The two wires are joined at one end to form the thermocouplejunction and the wires are attached at the opposite end to terminals l6and I8 respectively. The tube Ill is secured to a mounting flange bymeans of which the thermocouple may be attached to any selected portionof the exterior of the engine with the hot junction projected into thegas stream whose temperature is to be measured.

Specifically the supporting tube I0 is provided with a shoulder 2|adjacent one end thereof which provides a seat for a ceramic washer 22through which the wires I2 and [4 pass and are supported. An extension24 on the tube Ill extends beyond the shoulder 2| and has windows 28formed therein to permit the passage of gases transversely through theextension. The wires l2 and I4 extend from the interior of tube Illthrough the washer 22 and into the interior of the extension 24. Theportion of the wires in the extension 24 are welded together and areflattened to form a wide thin junction 25 which is the active portion orhot junction of the thermocouple. This junction 26 is bent into the formof a U with the thin edge of the junction 26 forming the face of the Uand is arranged with that thin edge facing the windows so that gasespassing transversely through the extension 24 by the way of the windowswill pass across the thermocouple junction 26 and. the thin edge of thejunction 26 will be facing the airstream. This arrangement will providea large area to mass ratio for the junction 26 which will give a fastresponse. The flattened number presenting the thin edge to the airstreamacts as a strength member to withstand the hot exhaust gas pressuresbecause the thin sections are directed into the exhaust stream.

The extension 24 acts as a radiation shield for the thermocouple unitpreventing both radiation from the hot joint and also preventingradiation from the turbine walls or the gas stream enclosure fromaffecting the thermocouple joint. The extension 24 also acts as aneffective protection against mechanical damage to the joint 26, eitherfrom objects in the gas stream or damage that might occur in handling orin installation or removal of the thermocouple.

The wires [2 and [4 are surrounded, within the tube Ill, by a pottingcompound 29, preferably Sauereisen cement, which will rigidly supportthe wires in the tube I0. Some of this cement finds its way around thewires in the ceramic washer 22 and acts to rigidly support the wires andthe junction 26 at a point adjacent to the junction 26.

Wires [2 and I4 pass through and are supported by a ceramic washer 30seated on a shoulder 32 adjacent the other end of the tube Ill.

The mounting flange 20, including a housing 34 projecting upwardlytherefrom, is Welded or otherwise secured to the end of the tube I0adjacent the ceramic washer 30. The wires l2 and 14 extend from the tubel0 through the ceramic washer 30 and into the housing 34 where they aresecured to terminal lugs I6 and [8 respectively. The lugs l6 and 18extend through ceramic washers 36, 38, 40, 42 and are supported by thoseceramic washers which in turn are supported by the housing 34 throughwhich both the terminal lugs l6 and I8 and the ceramic washers extend.

In use, the thermocouple may be mounted on a boss 44 located on ahousing or tube 46 through which the hot gases, whose temperature is tobe measured, are passing. The thermocouple may 3 r be secured to theboss 44 by cap screws 48 passing through the mounting flange 20. Thesupporting tube III carrying the hot junction 26 at the end thereofextends through the boss '44 and into the hot gas stream within thehousing 46.

In the manufacture of this thermocouple, one end of wire I2 is welded toone end of wire IA. The welded junction is then flattened and ground tothe desired size and finish. This junction is preferably formed so thatthe wires l2 and 4 lead from opposite ends thereof so that the junctionmay be bent into the form of a U and the wires brought into parallelrelation. It should be understood, however, that the junction may beformed so that both wires lead from one end of the junction and thejunction may be left straight or may be bent into any desired shape. Thewires extending from one end of the latter junction are, of course,already in parallel relation.

After the junction is formed, it is inspected and if found defective maybe discarded at this point without necessity of scrapping any of therest of the thermocouple. After inspection, ceramic washer 22 is slippedover the free ends of the wires l2 and 14 and placed firmly against theshoulder 50 at the flattened section v26, the wires passing throughsuitable holes in the washer 22. The wire and washer assembly is thenpassed through the end of the tube It] containing the shoulder 32 andthe washer 22 is seated against the shoulder 2l at the opposite end ofthe tube. A Meeting rod fittin both the windows 28 and the junction 26is passed through both the windows and the. junction to hold thejunction in line w th he Wind ws- The t be in containi th wire '2 andl4 1. 3116. filled W h a C ami potting cement 29 and the second ceramicwasher 3 is slipped over the free ends of the wires and P s into po i in a ain t the shoulders, forcing potting cement through the holes inwasher 22 and around the wires in those holes to securely anchor h ireI2 an i4 adjacent the hot junction,

After the potting cement hasset, the terminals 6 a d I8 and theirassoeia ed er m e washers r lid i o sl 52 in h h u ins 3 andi eu ed inposition by the nuts 5A, The wires !2 and M are then welde to theterminals 1.6 and 18- sp ine wa her '56 are util zed to ompen a for thedifier n e in xp ion etween the terminals l6 and I8 and the ceramicwashers through which they pass.

T h sin 34 i then completely fi led w h p t n mp und 2.9 and a cov r 58is tacked or bolted into place,

Although only one embodiment of this invention has been illustrated anddescribed herein, it will be apparent that various changes andmodifications may be made in the construction and arrangement of thevarious parts without departing from the scope of this novel concept.

What it is desired to obtain by Letters Patent is:

1. A thermocouple comprising a supporting member having an elongatedtubular portion, a pair of wires of dissimilar material extendingthrough, and projecting from one end of, said portion, and joined in theprojecting part to form the thermocouple junction, a potting cementfilling said tubular portion and closely surrounding both of said wiresto form a common ceramic support and rigidly support the wires in saidportion, said potting cement extending to a point adjacent said junctionto rigidly support said junction.

2. A thermocouple comprising a tubular supporting member having internalshoulders adjacent each end, a pair of wires supported in said tubularmember and projecting at both ends, projecting portions at one end beingjoined to form the thermocouple junction, an insulating washer, havingseparate perforations through which the wires pass, seated against theshoulder in one end of the tubular member and adjacent said junction tosupport said junction and locate said wires 'in-said tubular member, apotting compound substantially filling said tube and forcing said washeragainst its supporting shoulder and surrounding both said wires, asecond insulating washer through which the wires pass seated on theshoulder in the opposite end of said tube to locate said wires'in saidtube, terminal portions for said wires and mounting means for said tube.

3. A thermocouple comprising a tubular supporting member, a pair ofwiressupported in :said member and joined at one end to form thethermocouple junction, a common ceramic potting compound supportingsubstantially the entire length of both wires in said member leaving thejunction exposed, mounting means for said tube and lead wires connectedto said first-mentioned wires, a window formed in said tube walls adjacent said junction at one end of said tube, said junction comprising aflattened portion bent into a U-shape with the thin edge forming theface of the U and facing said window and with the wide sides of the Uadjacent the solid portion of the tube walls whereby the tube walls actas a radiation shield for said junction,

4. The method of making a thermocouple which comprises welding the endsof a pair of thermocouple wires to form a thermocouple junction,flattening said welded junction and then forming it into U shape bybringing the remainder of said wires into juxtaposed substantiallyparallel position, sliding said wires through the perforation of aperforated washer to a point adjacent said flattened junction, insertingsaid assembly intoa supporting tube with said washer seating on ashoulder and closing one end of said tube and locating the wires in saidtube, filling said tube with a potting material, sliding a second washeralong said wires and onto said potting material to close the other endof said tube and force potting compounds into theperforation in saidperforated washer and locate said wires in said tube .and then securingterminal portions onto said wires.

STANLEY G. BEST.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,289,116 Chubb o Dec. 31, 1:918 2,472,808 Dahl June 14, 19492,587,391 Sever Feb. 26, 1952 2,597,665 Nicholle May 20, 1952 OTHERREFERENCES Automotive "Industries, page '46, February 15, 1947.

